Homogeneity Of Electric Field Research Articles

Application of Gold Nanoparticles for Improvement of Electroporation-Assisted Drug Delivery and Bleomycin Electrochemotherapy

Background/Objectives: Electrochemotherapy (ECT) is a safe and efficient method of targeted drug delivery using pulsed electric fields (PEF), one that is based on the phenomenon of electroporation. However, the problems of electric field homogeneity within a tumor can cause a diminishing of the treatment efficacy, resulting only in partial response to the procedure. This work used gold nano-particles for electric field amplification, introducing the capability to improve available elec-trochemotherapy methods and solve problems associated with field non-homogeneity. Methods: We characterized the potential use of gold nanoparticles of 13 nm diameter (AuNPs: 13 nm) in combination with microsecond (0.6–1.5 kV/cm × 100 μs × 8 (1 Hz)) and nanosecond (6 kV/cm × 300–700 ns × 100 (1, 10, 100 kHz and 1 MHz)) electric field pulses. Finally, we tested the most prominent protocols (microsecond and nanosecond) in the context of bleomycin-based electrochemotherapy (4T1 mammary cancer cell line). Results: In the nano-pulse range, the synergistic effects (improved permeabilization and electrotransfer) were profound, with increased pulse burst frequency. Addi-tionally, AuNPs not only reduced the permeabilization thresholds but also affected pore resealing. It was shown that a saturated cytotoxic response with AuNPs can be triggered at significantly lower electric fields and that the AuNPs themselves are non-toxic for the cells either separately or in combination with bleomycin. Conclusions: The used electric fields are considered sub-threshold and/or not applicable for electrochemotherapy, however, when combined with AuNPs results in successful ECT, indicating the methodology’s prospective applicability as an anticancer treatment method.

Magnetic field and dielectric beads modulate DBD reduced electric field with discharge homogeneity to realize NOx differential conversion

In this paper, the reduced electric field and the discharge homogeneity of DBD were modulated by the magnetic field and the packed ZrO2 beads. Subsequently, the reduced electric field and the discharge homogeneity on discharge performance, de-NOx efficiency and NOx conversion mechanism were evaluated. The experimental results show that the reduced electric field gradually enhances as the magnetic field increases, promoting de-NOx performance. The discharge homogeneity significantly weakens with the length of packed ZrO2 beads increases, inhibiting the de-NOx performance. Compared to the reactor with the packed ZrO2 beads, the de-NOx efficiency of the reactor with a 0.2 T magnetic field can achieve 87.2 %, an improvement of 39.3 %. Meanwhile, the selectivity of NO2 and N2O are reduced by 18.3 % and 21 %, respectively. The de-NOx mechanisms indicate that the reduced electric field affects the electron collision reactions and the relative rate of the NOx conversion reactions by altering the electron energy distribution. The discharge homogeneity alters the degree of plasma mitigation of exhaust gases by regulating the absolute rate of the NOx conversion reactions. The by-product N2O is mainly dependent on the concentration of NO2 and is less sensitive to N2(A3). This work reveals the differential mechanisms of reduced electric field and discharge homogeneity on de-NOx.

Research on Electric Field Homogenization in Radial Multi-Nozzle Electrospinning.

Electrospinning is an effective method to prepare nanofibers at present. Aiming at problems such as low spinnable viscosity and the low productivity of the traditional multi-needle, a radial nozzle was proposed in this paper. In order to solve the problem of end effects in multi-nozzle electrospinning, COMSOL Multiphysics 6.0 software was used to simulate the electric field in electrospinning with seven radial nozzles. And the influence on the electric field intensity and distribution of the structural parameters of the radial nozzle, including the number, length, tip-shape, and tip-pointing direction of the vanes, were studied. Then, the electric field intensity of any point on the central axis of a radial nozzle was obtained based on the principle of electric field superposition, and then the rotation angle of the vanes corresponding to the minimum Coulomb repulsion force on the target point was deduced. At last, the method of electric field homogenization of a rotating vane arrangement was obtained. In the simulation, the strength and homogenization of the electric field were taken as the research objective, and the optimum structure parameters of the radial nozzle were obtained; the uniform theory of the electric field based on the orientation of the vanes was verified. Then, electrospinning with seven radial nozzles was performed, and it was found that each radial nozzle can produce multiple jets during electrospinning, and the prepared electrospun membranes have even thickness and high porosity. What is more, the fibers are relatively finer and more uniform.

Multifunctional Zincophilic Hydrogel Electrolyte with Abundant Hydrogen Bonds for Zinc-Ion Capacitors and Supercapacitors.

The new-generation flexible Zn-ion capacitors (ZICs) require multifunctionality and environmental adaptability for practical applications. This essentially means that hydrogel electrolytes are expected to possess superior mechanical properties, temperature resistance, and tunable interface properties to resist flexibility loss and performance degradation over a wide operating temperatures range. Herein, a multifunctional polyzwitterionic hydrogel electrolyte (PAM/LA/PSBMA) with wide operating temperatures, excellent tensile ability, high water retention, and self-adhesion is designed. Molecular dynamics simulations and experimental results show that polar functional groups (-COO-, -SO3-, -C═O, and -NHCO-) in the hydrogel can form abundant hydrogen bonds with water molecules, which can destroy the original hydrogen bonds (HBs) network between the water molecules and have a low freezing point. It can also form coordination with Zn2+, so that the deposition of Zn2+ electric field homogenization effectively alleviates the growth of Zn dendrites. On this basis, the constructed Zn//Zn cell can be stably cycled 290 h at 10 mA cm-2 (1 mA h cm-2). The constructed ZICs and supercapacitor have a high specific capacitance, excellent energy density, good ionic conductivity, and long cycling stability. This study provides guidance on molecular design for the development of integrated multifunctional smart electronic devices that are environmentally adaptable, resistant to drying, and highly flexible.

Spatiotemporally dynamic electric fields for brain cancer treatment: an in vitro investigation

Objective. The treatment of glioblastoma (GBM) using low intensity electric fields (∼1 V cm−1) is being investigated using multiple implanted bioelectrodes, which was termed intratumoral modulation therapy (IMT). Previous IMT studies theoretically optimized treatment parameters to maximize coverage with rotating fields, which required experimental investigation. In this study, we employed computer simulations to generate spatiotemporally dynamic electric fields, designed and purpose-built an IMT device for in vitro experiments, and evaluated the human GBM cellular responses to these fields. Approach. After measuring the electrical conductivity of the in vitro culturing medium, we designed experiments to evaluate the efficacy of various spatiotemporally dynamic fields: (a) different rotating field magnitudes, (b) rotating versus non-rotating fields, (c) 200 kHz versus 10 kHz stimulation, and (d) constructive versus destructive interference. A custom printed circuit board (PCB) was fabricated to enable four-electrode IMT in a 24-well plate. Patient derived GBM cells were treated and analyzed for viability using bioluminescence imaging. Main results. The optimal PCB design had electrodes placed 6.3 mm from the center. Spatiotemporally dynamic IMT fields at magnitudes of 1, 1.5, and 2 V cm−1 reduced GBM cell viability to 58%, 37% and 2% of sham controls respectively. Rotating versus non-rotating, and 200 kHz versus 10 kHz fields showed no statistical difference. The rotating configuration yielded a significant reduction (p < 0.01) in cell viability (47 ± 4%) compared to the voltage matched (99 ± 2%) and power matched (66 ± 3%) destructive interference cases. Significance. We found the most important factors in GBM cell susceptibility to IMT are electric field strength and homogeneity. Spatiotemporally dynamic electric fields have been evaluated in this study, where improvements to electric field coverage with lower power consumption and minimal field cancellations has been demonstrated. The impact of this optimized paradigm on cell susceptibility justifies its future use in preclinical and clinical trial investigations.

Integrated reactor architecture of conductive network and catalytic nodes to accelerate polysulfide conversion for durable and high-loading Li-S batteries

The development of carbon-based heterogeneous framework host with synergistic catalytic and conductive effects for sulfur cathode is a promising strategy to realize high performance lithium sulfur batteries (LSBs). Here, an integrated reactor architecture with defective carbon nodes (IRA-DC) is designed for serving as high-loading (92.4 wt%) sulfur host. The hierarchical porous IRA-DC consists of untangled conductive carbon nanotube network and Co/N co-doped catalytic nodes with high dispersity. Therein the optimization of electric field distribution and homogenization of adsorption-catalysis sites offer the multi-electron conversion reaction of polysulfides with excellent kinetics and stability. The resultant IRA-DC/S cathode enables a high areal capacity of 8.86 mAh cm−2 under ultra-high sulfur loading (13.1 mg cm−2) and lean electrolyte (8 μL mgsulfur−1). It also displays a long-term cycling performance (1200 cycles at 1 C) and ultrahigh rate performance up to 20 C (with a capacity of 473.6 mAh g−1). This work provides an electrode building strategy by optimizing the environments of heterogeneous electrocatalysis and micro electric field to activate the polysulfide conversion efficiency and utilization of high-loading sulfur in monolithic sulfur-carbon cathodes.

Design of the compact TPC for a high-precision 3D beam diagnostic system

A compact Time Projection Chamber (TPC) with a gas electron multiplier (GEM) is a good candidate for three-dimensional (3D) beam diagnosis of electron and ion beams. To develop the beam diagnostics, we performed simulation studies to design a compact GEM-TPC with COMSOL and GARFIELD++. The primary purpose of this detector is to measure the 3D beam profile at the medical cancer center, which requires a position resolution of ∼300μm in each coordinate and can accommodate a proton rate of 104 s−1. For the design of the detector that satisfies the requirements, the simulations were done on the electric field homogeneity of the cylindrical field cage, the transport properties, and the amplification of electrons in the argon-based gases. This paper presents the design parameters of the compact TPC for constructing a high-precision 3D beam diagnostic system derived from COMSOL and GARFIELD++ simulations.

Design considerations for a cycloidal mass analyzer using a focal plane array detector.

With the advent of technologies such as ion array detectors and high energy permanent magnet materials, there is renewed interest in the unique focusing properties of the cycloidal mass analyzer and its ability to enable small, high-resolution, and high-sensitivity instruments. However, most literature dealing with the design of cycloidal mass analyzers assumes a single channel detector because at the time of those publications, compatible multichannel detectors were not available. This manuscript introduces and discusses considerations and a procedure for designing cycloidal mass analyzers coupled with focal plane ion array detectors. To arrive at a set of relevant design considerations, we first review the unique focusing properties of the cycloidal mass analyzer and then present calculations detailing how the dimensions and position of the focal plane array detector relative to the ion source determine the possible mass ranges and resolutions of a cycloidal mass analyzer. We present derivations and calculations used to determine the volume of homogeneous electric and magnetic fields needed to contain the ion trajectories and explore the relationship between electric and magnetic field homogeneity on resolving power using finite element analysis (FEA) simulations. A set of equations relating the electric field homogeneity to the geometry of the electric sector electrodes was developed by fitting homogeneity values from 78 different FEA models. Finally, a sequence of steps is suggested for designing a cycloidal mass analyzer employing an array detector.

Distortion of electric field homogeneity between two thin toroidal electrodes by a dielectric sphere

We assess the influence of a radius and a relative permittivity of an isotropic dielectric sphere on electric field homogeneity. The homogenous electric field is generated using two thin toroidal electrodes, charged by equal charges of opposite signs. The Poisson equation is solved by a method of separation of variables. Increase in a relative permittivity of the sphere and in its radius, produces more distortions of the electric field homogeneity.

Modeling and design of a new conductance probe for Gas Void Fraction measurement of two-phase flow through annulus

Gas-liquid two-phase flow in annulus channels is encountered in several industrial applications, and the Gas Void Fraction (GVF) measurement of such flow is crucial for either monitoring or controlling processes. However, the challenging constraints surrounding annular channels, such as the relatively small distance between the inner and outer pipelines and the non-intrusive accessibility to the inner pipeline, made the GVF measurement difficult to be handled using existing GVF measurement techniques. This paper suggests a new multi-electrodes conductance probe to accurately measure the GVF within annulus flow. The design was finalized after several iterative tunings, followed by an optimization step where a new objective function was suggested to maximize the measurement sensitivity by searching for the optimal relative placement of the electrodes. This was facilitated using COMSOL Multiphysics software, where extensive numerical simulations were done on two types of conductance probes. This has led us to conclude that the new suggested conductance probe, namely 2.2RE probe, which consists of 2×2 ring electrodes, can yield a high measurement sensitivity within the target sensing domain, in terms of electric field homogeneity and concentration, using a reasonable amount of hardware compared to other previous works. Indeed, two-dimensional (2D) and three-dimensional (3D) visualization of the current streamlines showed the ability of the 2.2RE probe to handle more efficiently different two-phase flow configurations in the annulus. Furthermore, the geometry of the 2.2RE probe was optimized after a comprehensive analysis of the probe dimensions’ effect on its performance. Series of experiments were conducted on a 2.2RE prototype which was designed according to the optimal dimensions to assess the probe response for bubbly and annular flow patterns. The maximum GVF value which was experimentally considered for bubbly and annular patterns were 0.31 and 0.95, respectively. The 2.2RE probe showed a slight dependency on the flow pattern where it exhibited a linear and quasi-linear relationships of the probe output voltage function of the GVF for bubbly and annular flow patterns, respectively. The comparison of experimental and numerical data revealed that the numerical model matches well the experimental data with a maximal relative error of 7.32%. A calibration procedure of the 2.2RE probe was initiated and assessed numerically, and an accurate estimation of the GVF could be achieved.

Fabrication of Ag@BaTiO3 hybrid nanofibers via coaxial electrospinning toward polymeric composites with highly enhanced dielectric performances

Here we demonstrated a remarkable improvement in the dielectric performance of poly (vinylidene fluoride) (PVDF)-based composites via incorporating distinguished hybrid nanofibers, namely, Ag nanoparticles-embedded BaTiO3 (Ag@BaTiO3, Ag@BT) nanofibers, which were fabricated by coaxial electrospinning technology followed by calcination. The Ag nanoparticles on BaTiO3 nanofibers were found to play a comprehensive role on the dielectric performances, including the better dispersion of hybrid nanofibers leading to homogeneity of electric field, the formation of charge transfer complex in the hybrid region which enhanced the interfacial polarization, and the Coulomb blockade effect of Ag nanoparticles to further suppress the interfacial charge accumulation. As a result, the PVDF/Ag@BT composites exhibited high dielectric constant of 38.87@1 kHz and low loss of 0.02@1 kHz.

Effects of surface conductivity on surface charging behavior of DC-GIL spacers

In this study, a simulation model is established to study the effect of surface conductivity on the accumulation of surface charge. The simulation shows that hetero-charges increase on areas away from the high voltage electrode and the electric field distribution along the surface becomes more uniform with increased surface conductivity. The dominant surface charging mechanism changes from conduction through the bulk of the insulation to surface conduction with increased surface conductivity. When the surface conductivity ranges from 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> to 5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-14</sup> S for a convex spacer surface, an optimal surface charge suppression and electric field homogeneity can be realized.

An ultrathin ionomer interphase for high efficiency lithium anode in carbonate based electrolyte

High coulombic efficiency and dendrite suppression in carbonate electrolytes remain challenges to the development of high-energy lithium ion batteries containing lithium metal anodes. Here we demonstrate an ultrathin (≤100 nm) lithium-ion ionomer membrane consisting of lithium-exchanged sulfonated polyether ether ketone embedded with polyhedral oligosilsesquioxane as a coating layer on copper or lithium for achieving efficient and stable lithium plating-stripping cycles in a carbonate-based electrolyte. Operando analyses and theoretical simulation reveal the remarkable ability of the ionomer coating to enable electric field homogenization over a considerably large lithium-plating surface. The membrane coating, serving as an artificial solid-electrolyte interphase filter in minimizing parasitic reactions at the electrolyte-electrode interface, enables dendrite-free lithium plating on copper with outstanding coulombic efficiencies at room and elevated (50 °C) temperatures. The membrane coated copper demonstrates itself as a promising current collector for manufacturing high-quality pre-plated lithium thin-film anode.

Nonlinear Electrical Properties and Field Dependency of BST and Nano-ZnO-Doped Silicone Rubber Composites

Recently, composite materials with nonlinear dielectric or resistive properties performed well in electric field homogenization and space charge suppression in a high voltage transmission and distribution system. For the purpose of obtaining insulation materials with desirable dielectric and electrical resistance properties, we investigated several fillers with nonlinear electrical properties doped in silicon rubber composites, and their dependency on the temperature and field. The samples of silicone rubber composites with different components were prepared using barium strontium titanate (BST) and zinc oxide (ZnO) as the filler, and high temperature vulcanized silicone rubber (SiR) as the matrix. The investigations revealed that the BST-doped samples showed different dielectric properties compared to ZnO-doped composites, with an increase in the electric field, which was nonlinear. The resistivity of both doped samples was similar. Results demonstrated that it was possible to achieve higher values of permittivity, and lower values of tanδ and resistivity, with respect to unfilled silicone rubber composites over a wide electrical field and temperature range. Discussion of the results attributes these important functional behaviours to the spontaneous polarization of nonlinear nanoparticles and the interaction between the SiR chains and the nonlinear nanoparticles at the interfacial area.

A sparkless resistive glass correction electrode for the spherical proportional counter

A new anode support structure for the spherical proportional counter is presented that incorporates a resistive correction electrode made of glass. This electrode improves the electric field homogeneity versus angle, while suppressing the probability and intensity of sparks compared to non-resistive alternatives. The configuration of the correction electrode was optimised with simulations. Such support structures have been constructed and measurements have demonstrated homogeneous response of the detector and operational stability. A measurement of the resistivity of the glass used is also presented.

Synthesis of Electrode Configurations that Conserve Fringing Electric Field Homogeneity in Euler Terms

Electric fields that are homogeneous in Euler terms are useful tools for synthesizing electron–and ion–optical systems with unique properties. However, fringing electric fields usually disturb the ideality of theoretically devised schemes. A way of synthesizing fringing fields is suggested that conserves their homogeneity in Euler terms, and hence, conserves theoretically predicted optimal characteristics of corresponding electron–and ion–optical systems.

Applications of High and Ultra High Pressure Homogenization for Food Safety.

Traditionally, the shelf-life and safety of foods have been achieved by thermal processing. Low temperature long time and high temperature short time treatments are the most commonly used hurdles for the pasteurization of fluid foods and raw materials. However, the thermal treatments can reduce the product quality and freshness. Consequently, some non-thermal pasteurization process have been proposed during the last decades, including high hydrostatic pressure, pulsed electric field, ultrasound (US), and high pressure homogenization (HPH). This last technique has been demonstrated to have a great potential to provide “fresh-like” products with prolonged shelf-life. Moreover, the recent developments in high-pressure-homogenization technology and the design of new homogenization valves able to withstand pressures up to 350–400 MPa have opened new opportunities to homogenization processing in the food industries and, consequently, permitted the development of new products differentiated from traditional ones by sensory and structural characteristics or functional properties. For this, this review deals with the principal mechanisms of action of HPH against microorganisms of food concern in relation to the adopted homogenizer and process parameters. In addition, the effects of homogenization on foodborne pathogenic species inactivation in relation to the food matrix and food chemico-physical and process variables will be reviewed. Also the combined use of this alternative technology with other non-thermal technologies will be considered.

Endovascular Electrodes for Electrical Stimulation of Blood Vessels for Vasoconstriction - a Finite Element Simulation Study.

Hemorrhagic shock accounts for 30–40 percent of trauma mortality, as bleeding may sometimes be hard to control. Application of short electrical pulses on blood vessels was recently shown to elicit robust vasoconstriction and reduction of blood loss following vascular injury. In this study we present a novel approach for vasoconstriction based on endovascular application of electrical pulses for situations where access to the vessel is limited. In addition to ease of access, we hypothesize that this novel approach will result in a localized and efficient vasoconstriction. Using computer modeling (COMSOL Multiphysics, Electric Currents Module), we studied the effect of endovascular pulsed electrical treatment on abdominal aorta of pigs, and compared the efficiency of different electrodes configurations on the electric field amplitude, homogeneity and locality when applied on a blood vessel wall. Results reveal that the optimal configuration is the endovascular approach where four electrodes are used, spaced 13 mm apart. Furthermore, computer based temperature investigations (bio-heat model, COMSOL Multiphysics) show that the maximum expected temperature rise is of 1.2 degrees; highlighting the safety of the four endovascular electrodes configuration. These results can aid in planning the application of endovascular pulsed electrical treatment as an efficient and safe vasoconstriction approach.

An HF exposure system for mice with improved efficiency.

An exposure system that addresses difficulties that arise for exposure of small animals at low frequencies with a high exposure level is presented. The system, intended to operate at 27 MHz, consists of two identical transverse electro-magnetic (TEM) cells for exposure and sham exposure of groups of 16 free-running mice housed in pairs within standard cages, capable of exposure over extended daily periods while being provided food and water. Inclusion of the exposure cell in a half-wavelength resonator has been developed as a new paradigm to enhance field strength for an increase of >50-fold in available specific absorption rate (SAR) levels compared to traditional TEM cell configurations. The system described allows both daily and weekly exposure schedules and supports blinded protocols with continuous wave (CW) and amplitude modulation (AM) signals with programmable modulation depths and frequencies. Electric field (E-field) homogeneity across the TEM cell along a vertical plane (orthogonal to the axis of the TEM line) was within 3.3%, and 3.1% along the horizontal plane. Accurate and comprehensive dosimetric assessments based on whole-body and organ-specific SAR essential for in vivo bioelectromagnetic experiments are presented, which takes into account various factors (e.g., mouse activities, close proximity, and field homogeneity). Average SAR levels are controllable in the range of 1 mW/kg to 2 W/kg, with expanded uncertainty (k = 2) of 1 dB and instantaneous variation (k = 1) of 4 dB.

Conductive Gel Increases the Small Tumor Treatment With Electrochemotherapy Using Needle Electrodes.

The combination of chemotherapy drugs and high electric field treatment in local cancer is named electrochemotherapy. The European Standard Operation Procedure of Electrochemotherapy (ESOPE) provides guidelines for treatment of cutaneous and subcutaneous tumors. The electrochemotherapy of numerous tumors varying in sizes is more convenient using needle electrodes. However, ESOPE recommends that needle electrodes are applied to deeper tumors. The application of needle electrodes to treatment of superficial small tumors seems to be practical in electrochemotherapy. Plate electrodes and gel improve the electrochemotherapy efficacy. This technique provides electric field homogeneity in irregularly shaped tissue structures (bulk tumors). We propose an investigation of needle electrode and gel in electrochemotherapy of superficial tumors. In vivo experiment with squamous cell carcinoma (SCC) spontaneous nodules in dog was used to validate the mathematical tissue model. The numerical model considers the tissue conductivity dependent on local electric field. Our studies demonstrated that conductive gel is important for effective treatment of superficial tumors with needle electrodes. The needle electrodes and gel presented reduction of medium current, increased the tumor-free margin, and improved the practical application in relation to plate electrode.